| Conventional pollutants are the main concern of gas pollution control in our country, such as TSP, SO2, NOx, fewer concerns about heavy metals pollution in them. In this paper, part of the coal-fired plant in Xinjiang were as the object, studies of heavy metal distribution in this coal-fired power plants were carried out; Gas boiler of Urumqi was for the object, research of natural gas boiler emissions of mercury was carried out, the main findings are as follows:(1)The emission data of of nine kinds of heavy metals in four coal-fired power plants’ flue gas by method of EPA29.Concentrations of heavy metals in four power plants in this article are low compared with the literature.There’s the maximum enrichment factor in the fly ash with each element,the fly ash could easily accumulated heavy metals.ESP could remove most heavy metals produced by the combustion of coal.The balance rates of four plants of each element are between in 70% to 120%. Heavy metals such as Co, Cr, Cu, Ni, Pb, Zn, Cd and As are mostly enriched in the fly ash and desulfurization ash, Desulfurization gypsum can only enrichs mercury and its compounds, as for the elements such as Co, Cr, Cu, Ni, Pb, Zn, Cd and As,there shows no enrichment.(2)The study of the nine elements include Hg, As, Pb, Co, Zn, Ni, Cd, Cu and Cr on 12 coal mines and 23 coal-fired enterprises in in Urumqi found that: the content of each element are in rang of the element in coal s of China,the content of Cu and Cr are slightly higher than the average dates of Chinese coal,the average dates of other elements in coal is lower than the average dates of Chinese coal.(3)By setting up device of mercury releases,get a reliable,simple,excellent operational method.By this method to carry out the release of test of two coal samples that have higher levels of mercury in Urumqi coal mines,the results showed that when the release temperature ≥700 ℃, release temperature ≥30min,the releasing of mercury in coal was completely, there were similar releasing rule compared with other high mercury coal samples in the rest of the regions of our country.(4)The mercury of Urumqi boiler flue gas are gaseous mercury, the main form of which is elemental mercury.Compared with coal-fired boilers,natural gas is a clean fuel,mainly due to the conventional pollutants of natural gas decreased significantly, especially in emissions of soot and SO2.But the content of mercury in natural gas can not be discounted. If mercury input is not considered combustion of air, the concentration of mercury in natural gas in Urumqi was 26.62-31.44 μg/Nm3.Compared with the mercury content data of China’s eight basin gas,mercury levels are moderately low level.the emissions intensity of mercury in Urumqi flue gas is(0.00079-0.00093)×10-12g/J,far less than the total mercury emissions intensity from coal-fired power plants(0.77 ~ 0.81)×10-12g/J.Coal to gas can reduce mercury emissions in the flue gas.(5)Add combustion supporting agent can reduce the ignition temperature,burnout temperature and relative burn time.Experimental results from the combustion accelerant content works best at around 1.5‰.Combustion of coal-fired combustion rate can be increased and at the same time, reducing the coal consuption of coal-fired enterprise, while reducing the emissions of heavy metals caused by coal-fired. |
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